In applicator devices which comprise an applicator beam oriented transverse to the running direction of the web, and to which beam the coating-agent coating-nozzle device, coating head or equivalent has been attached, it is a significant problem that the size, paste or equivalent coating material is fed into the nozzle device or coating head at a very high temperature, whereas normally the temperature of the applicator beam itself is substantially lower. Owing to this temperature difference, considerable bending and distortion have occurred in the applicator beam and in the nozzle device itself, in which case it has been very difficult to produce an even, uniform layer of coating agent on the moving base being coated. In the prior art, attempts have been made to solve this problem, for example, so that the temperature of the applicator beam itself has been raised considerably, whereby the difference in temperature between the applicator beam and the nozzle device has thereby been reduced considerably, and therefore the extent of bending has been lower. From the point of view of the process itself, such a solution is, however, not advantageous, because the applicator beam itself should preferably be kept at a temperature as low as possible.
It is a second solution to this problem that, in order to correct the distortion of the beam arising from tensions resulting from thermal expansion (resulting from the temperature difference), the applicator beam itself has been bent in different ways. One such solution is described, among other things, in Finnish Patent Application No. 882368, in which a measurement device is arranged inside the applicator beam so as to measure the bending of the beam, together with an aligning device by whose means the bending of the beam is corrected based on the information provided by the measurement device. Another comparable solution is described, for example, in German Utility Model Publication No. 9,207,551, in which the applicator beam is provided with a hydraulic actuator, by whose means the applicator beam is bent in order to correct the bending arising from differences in temperature. However, these prior art solutions are not very good or advanced because the emphasis has merely been mainly on correcting of the distortions arising from thermal strains, and no attention whatsoever has been paid to elimination of the thermal strains themselves. In other words, they are directed to correcting the problem after it has already arisen as opposed to avoiding the occurrence of the problem.